Electronic devices such as RF (Radio Frequency) receivers, transmitters and various other devices include a VCO operating within a PLL (Phase Locked Loop) to maintain a desired oscillation frequency.
It is conventional practice to tune a VCO to a particular initial frequency before it leaves its factory. This is typically accomplished by using factory equipment to measure the frequency of the VCO while it is free-running (i.e., the PLL is opened), and laser-trimming a capacitor or other circuit element that modifies the frequency of the VCO. An additional trim of the bias applied to the VCO is sometimes used to provide improved SBN (Side Band Noise) performance.
The conventional practice described above has several disadvantages: it uses costly tuning equipment that requires extra space in the factory, and it is a relatively time consuming procedure.